German scientists were working on Monday to confirm an organic vegetable farm as the source of an outbreak of E.coli bacteria that has killed 22 people and caused a food scare across Europe.

German scientists were working on Monday to confirm an organic vegetable farm as the source of an outbreak of E.coli bacteria that has killed 22 people and caused a food scare across Europe.

E.coli tests on 23 of the 40 samples of beansprouts from the farm in north Germany have proved negative, and the tests are not expected to be completed in the short term, the ministry said in a statement.

The manager of the farm said he could not understand how it could be the source of an infection that is usually transmitted through faeces, or food or water contaminated with faecal bacteria. The Shiga toxin-producing E.coli strain found in this outbreak is known to be able to lurk in cows' intestines.

Scientists say the contamination may have been on or in the bean seeds themselves, in the water used to grow them, or have come from a worker handling them.